Membership allowing user to be overwritten

Hi guys...

 I am a new member on this forum and I am wondering about what is wrong with this code:  protected void db_CreateUser()
{
String username = usernamebox.Text.ToLower();
String emailaddr = emailbox.Text.ToLower();
String password = PasswordBox1.Text;
String organizationName = OrganizationName.Text;
String suborgName = SubOrganizationName.Text;
String ownerName = OwnerName.Text;
String secretQuestion = SecretQuestion.Text;
String secretAnswer = SecretAnswer.Text;
String countryCode = Country.Text;
String stateCode = State.Text;

MembershipCreateStatus MemberStatus = new MembershipCreateStatus();

try
{
Membership.ApplicationName = "SurveyMatch";
Membership.CreateUser(username ...